The invention relates generally to genetic engineering and, more particularly, to a means and method for making plants which produce substantially seedless fruit, wherein the seedless fruit has desirable taste and size characteristics, rendering it more appealing than naturally occurring fruit to the consumer.
Parthenocarpy, the production of seedless fruits, can be achieved by the addition of the plant growth regulators auxin, cytokinin or gibberellin in many crop species (see, e.g., Naylor (1984) in Hormonal Regulation of Development II: the functions of hormones from the levels of the cell to the whole plant, Scott, T., ed., pp. 172-218, Springer-Verlag). Applications of these hormones to the unfertilized flowers of tomato, pepper, tobacco, holly, fig, cucumber, watermelon, avocado, eggplant, pear, blackberry and many other species, induced fruit set in the absence of pollen.
It has been shown that the exogenous application of auxin or gibberellin to unfertilized flowers in a number of plant species, including tomato (Lysopersicon esculentum) induces fruit set in the absence of pollination, resulting in the production of parthenocarpic fruit [Wareing and Phillips (1981) Growth and Differentiation in Plants, Pergamon Press, Oxford, UK]. By contrast, the exogenous application of cytokinin to ovaries or developing fruits is less effective for the production of seedless fruits. It is believed that exogenously applied cytokinin cannot reach the site of action for fruit development because the hormone is immobile within the plant.
In previous efforts to produce seedless fruits, traditional plant breeding and exogenous application of hormones have been used with some success. However, the exogenous application of plant hormones is a labor-intensive process, and traditional plant breeding is a long term process. Moreover, at least some of the previous attempts to produce certain seedless fruits have resulted in low numbers of seedless fruits and/or in relatively small seedless fruits as compared with the normal, seeded fruits.
There is a long felt need in the art for an effective and economical means and methods for the production of seedless fruit, particularly in good yield and quality as compared with prior art seedless fruits.